Field of the Invention
The field of the invention relates to heat sinks, and more particularly to heat pipes for use in aviation and aerospace.
Description of the Related Art
Passive heat transfer systems are not typically used in today's aeronautic platforms due to hydrostatic pressure requirements for such systems. For example, heat pipes using an internal wick structure for return of a working fluid from an evaporator end to a condenser end, such as that illustrated in FIG. 1, may suffer from a high hydrostatic pressure drop when subjected to the high gravity (g) forces that may be experienced by such heat pipes when used in aircraft or aerospace vehicles. The g forces may significantly increase flow resistance for liquid returning to the evaporator (see also FIG. 2) to a point where capillary pumping pressure may not be sufficient to maintain adequate flow of the working fluid. Phase change heat transfer performance is significantly weakened by the poor working liquid supply, thereby motivating designers of heat transfer systems to use alternative technologies. In general, it is estimated that no practical heat pipe system using vapor-chamber technology may work against gravity up to 9g. Although unfavorable, liquid cooling or unreliable fan cooling systems become the only choices for aeronautic thermal solution. Liquid cooling approaches use a pump to circulate WEG liquid between the hot sources and heat sink. Unfortunately, the weight of WEG liquid, along with the electrical pump, sacrifices the airplane payload and electrical energy consumption. Fan cooling approaches are notorious for their low heat transfer effectiveness. In general, the heat transfer coefficient of forced air convection is one order of magnitude lower than liquid convection or phase change heat transfer. Fan cooling is also an unreliable thermal management approach, proven by numerous cases in the electronic industry.
Thus, there is a critical need to provide evaporative cooling of a heat source such as power electronics in a high-gravity (g) environment without consuming excess electrical power and without introducing unnecessary weight.